1. Field of the Invention
The present invention relates to a plasma etching chamber and a method for manufacturing a photomask using the same, and more particularly, to a plasma etching chamber of a plasma etching device used in an etching process for manufacturing a photomask and a method for manufacturing a photomask using the same.
2. Description of the Related Art
A photomask is typically used in a photolithographic process for manufacturing a semiconductor device, and the photomask may have various exposure patterns to achieve the desired result. To form a photomask having a desired exposure pattern, a shading layer is first formed on a photomask substrate, and a photoresist pattern is formed on the shading layer to expose a portion of the shading layer to create a shading layer pattern.
In general, photomask substrates are square-shaped. When the photoresist layer is formed on a square-shaped photomask substrate, a portion of the photoresist layer at the corners of the photomask substrate is thicker than a portion of the photoresist layer near the center of the photomask substrate. For example, in the case of forming an electron beam photoresist layer to a thickness of 3000 Å, the electron beam photoresist layer at the corners of the photomask substrate is about 200 Å thicker than the electron beam photoresist layer at the center of the photomask substrate.
Given this non-uniformity, after electron beam exposure and development are performed on the resultant substrate, the critical dimension (CD) of a portion close to the edge of the photomask substrate becomes smaller than that of a portion close to the center of the photomask substrate. Indeed, based on an after development inspection (ADI) performed after the photoresist layer pattern is formed to partially expose the shading layer on the photomask substrate, it has been noted that portions closer to the edge of the photomask substrate exhibit a smaller CD value.
Moreover, after the shading layer is etched by dry etching using the photoresist layer pattern as an etching mask, the difference in the CD among portions of the photomask substrate is even more pronounced. More specifically, the shading layer is etched to form a shading layer pattern, and then stripping and cleaning processes are performed on the resultant substrate. After that, an after cleaning inspection (ACI) is carried out. With reference to the ACI, the difference in the CD among portions of the shading layer pattern is more pronounced, because an etching rate for the shading layer at the center of the photomask substrate is relatively high, whereas an etching rate for the shading layer at the edge of the photomask substrate is relatively low.
As described above, if a photomask having a predetermined exposure pattern and exhibiting non-uniform CD distribution over an entire photomask substrate is used in the manufacture of semiconductor devices, various problems may occur, including performance degradation or inoperative devices.